The need for developing large clamping forces in connectors for securing two members together has long been recognized. Providing large clamping forces is especially important when the connector is to be used for connecting two tubular members of an underwater well installation, since the connection must then withstand not only large forces resulting from component weight and the actions of waves and currents but also large internal fluid pressures. All of the successful prior-art connectors employed in the underwater well field for developing high clamping forces appear to employ annular locking means, varying from annularly arranged collets or segments to a single split locking ring, the locking means being carried by one of the members to be connected and having a frustoconical locking shoulder to engage with a mating shoulder carried by the other member. Opposed transverse end surfaces are provided, and the effect of the locking means, when actuated, is to clamp the end faces together, the locking shoulders providing a strong wedging action to generate the clamping force. In such connectors, actuation of the locking means is accomplished by a rectilinear power device which acts in a direction generally axially of the connector. To convert the action of the power device into effective movement of the locking means, it has become a standard practice to have the power device force a driving ring axially relative to the connector, the driving ring having a frustoconical camming face which slidably engages the locking means to force the locking means generally radially and thus cause the desired wedging action at the locking shoulder.
A particular problem posed by the need for very large clamping forces in such connectors arises because, on the one hand, the power available from acceptable power devices is limited by size constraints while, on the other hand, losses due to friction at the camming surfaces demand large actuating power if operation of the locking means is to result in the desired large clamping forces. Accordingly, as disclosed in aforementioned application Ser. No. 327,449, such connectors have been improved by providing rolling antifriction elements between the camming surface of the driving ring and a cam follower surface on the locking means. While this improvement makes it possible to achieve marked increases in efficiency and therefore employ smaller power devices, a problem is presented because of the axial length of the camming surface driven by the power device and the difficulty of adequately confining the antifriction elements without introducing sliding friction.